This NINDS-supported Core (formerly called BAG Engineering Technology) has been in operation for nine years under the direction of Dr. JrGang ,Cheng, a pioneer in the field of BAC recombineering. Over this time, our Core established a local and national reputation for excellence in generating BAC transgenes and gene-targeting constructs (Essential function #1 below, Figs. 1.1 & 1.2). To capitalize on the molecular expertise of the core and economies of scale, we propose to expand its essential functions (to include items #2-4 below) in this renewal period.